Most French fried potatoes produced within the process food industry have been prepared in a sequence of steps including the cutting of whole potato into a multiplicity of potato strips which are then blanched in hot water. A water removal or drying step follows which employs circulating air to remove surface water from the strips as well as a predetermined, partial removal of internal water prior to depositing the strips into a vat of hot cooking oil for a time period sufficient to reduce the moisture content of the potato strips to fall within a predetermined internal moisture range. Following removal from the cooking oil the strips are transferred to a quick freezer and then packaged for later finish frying before serving to customers. Some French fries are not frozen but chilled to be consumed within a short period after processing, usually not more than a few days. Other fries may not be processed by blanching and drying.
The prior art may embrace cooking of potato products as thin slices which float while frying, resulting in potato chips, a thin, dry brittle product. This is contrasted to cooking potato strips which sink while frying, resulting in the characteristic French fried potatoes which have body. In either field the frying step may occur in deep-frying apparatus having a vat to contain a volume of cooking oil with means serving for oil inputs and discharge including provisions for cooking oil re-heating and re-circulation with appropriate controls for cooking oil temperatures and product dwell time. The potato products were deposited in and removed from the vat of cooking oil via conveyors of various types or impelled along a process path by mechanical stirrers. In the case of potato strips the process time in the cooking oil was relatively short, as the finished moisture content of French fries falls in the range of 62% to 68%. This contrasts with potato slices which require substantially longer times in the cooking oil, the finishing moisture content of the resulting potato chips falls in the range of 1½% to 2%.
The Benson et al. U.S. Pat. No. 5,580,598, granted Dec. 3, 1996, disclosed flexibility in changeover from one processing method and product to another and taught mechanical means for stirring the products in the cooking oil as well as for urging the products along the processing path. The products and cooking oil moved concurrently through the cooker, being that cooking oil was introduced at the product feed end of the vat and removed at the product discharge end.
The Benson et al. U.S. Pat. No. 5,167,979, granted Dec. 1, 1992, disclosed control of the time-temperature curves in cooking oil to achieve various styles of potato chips from potato slices. These were moved along the processing path and agitated by mechanical means. Cooking oil inlets and outlets were shown arranged in the cooker bottom but it was not taught that the oil flow would determine the orientation of the potato slices during the cooking cycle, the mechanical agitating means determining that function.
The Haraldsson et al. U.S. Pat. No. 5,865,102, granted Feb. 2, 1999, disclosed deep frying potato slices in a pan having a plurality of cooking oil inlets and a plurality of cooking outlets, all located in the bottom of the pan. Lateral oil inlets were positioned in the sides of the pan to create turbulence in the cooking oil transversely of the longitudinal direction of the pan. The concept was to use turbulence to encourage separation of the potato slices while cooking in oil. Orientation of the slices in the cooking oil was not taught nor was control of steam generated from the cooking potato slices.